Developing a firewall application in C#

that will be quite hard to do because AFAIK you won't be able to bind your c# apps to ports that are already in use etc.
You could look at the pcap lib or something like that but are you sure you want to write a firewall yourself when there are so many well tested solutions?
http://www.tcpdump.org/pcap.htm

Well I'm not writing a firewall to compete with other companies :) It's my graduation project (I'm a computer science student).

I think you need to look for a packet capture library or write one on your own, preferably in a more low level language. Then use those captures in a c# app an check them against rulesets.
Watch out for buffer checking and strcpy etc in the low level lib if you write it yourself.

Did you pick that grad project yourself or was it assigned? Either you are a glutton for punishment or your teacher is crazy

Thanks for your replies, actually I did choose my graduation project and it was the firewall, and an antivirus application too.

I think it will be ok to write a packet capture library in a low level language, if you know any resources that can help me with that I will be grateful.

Thanks again,
Wessam Fathi

I don't know about any good resources that you can't google up, the only lib's I know of are pcap and ethereal